Email Marketing

Which is the Best Subject Line Testing AI Software?

Revolutionize Email Marketing with AI Subject Line Tools


Hafsa Channa


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Finding the perfect subject line for your email campaigns can be daunting. With hundreds of emails going out each day and effective emails relying on succinct messaging, it’s essential to make sure that you’re getting the most out of your efforts.

As Artificial Intelligence (AI) continues to evolve, AI-based software is being specifically designed to test subject email lines—but which one should you choose?

In this blog post, we are looking at some popular email subject line testing tools to help you find the best subject line testing ai software for your email campaigns. Read on as we dive into what makes these different solutions stand out and offer advice on how you can use them to continue improving your emails' performance!

Also Read: Are You Doing Something Wrong When Writing Catchy Subject Lines for Sales?

"As the Roman philosopher Seneca said, 'Luck is what happens when preparation meets opportunity.' 

By using a subject line testing AI software, you're preparing yourself for success and maximizing the opportunities available to you.

Refine by Moosend

subject line testing AI software - Moosend

Moosend has crossed 1000+ reviews till now. Moosend provides a free browser tool called Refine for creating email subject lines. Refine provides data specific to your industry and subscriber list, so you can optimize your subject lines. 

For instance, It simplifies the process of predicting open and click rates. 

Simply input a subject line, and AI technology will predict your performance and compare it to industry averages, indicating whether you'll fall below, meet or exceed average performance. Additionally, Refine provides tailored recommendations. 

For instance, it may suggest including your brand name or other personalized fields.


  • Moosend offers customizable forms and landing pages.

  • Moosend's campaign builder tool enables users to create and manage targeted email campaigns. 

  • It offers automation builders to users to set up workflows for personalized emails based on user behavior, engagement, and other criteria.

  • Moosend offers a variety of list management and segmentation tools.

  • It allows personalization of email marketing campaigns using dynamic content, custom fields, etc. 

  • It offers integration with a number of apps and tools.


  • Create customizable forms and landing pages to engage your audience.

  • Target specific audiences with personalized email campaigns using the campaign builder tool.

  • Organize your email lists with list management and segmentation tools based on different criteria such as gender, age, and location.

  • Personalize email campaigns with dynamic content and custom fields for a more engaging experience.

  • Seamlessly integrate with popular apps and tools such as Shopify, Wordpress, Salesforce, and Zapier.


  • Lacks a website builder.


subject line testing AI software Moosend pricing

Send Check It

subject line testing AI software - send check it

According to a recent study, emails with personalized subject lines have an open rate of 50%, compared to non-personalized emails with an open rate of 14.1 %. 

As email marketing becomes increasingly important in today's digital age, finding ways to stand out from the competition is crucial. 

The Send Check It AI subject line tool tester is a relatively new tool, and it's still building its customer base and reputation. Send Check It offers many email testing tools, including pre-send email testing, HTML validation, spam testing, accessibility testing, and sender reputation scoring. 


  • Send Check It allows you to test your email content, including subject lines, email body, and attachments.

  • It allows preview across browsers and devices.  You can preview how your email will look on different email clients, devices, and browsers.

  • It offers HTML validation.

  • Send Check It tests your email content against various spam filters.

  • Send Check It checks your email content for accessibility compliance, ensuring it's accessible to subscribers with disabilities.

  • It provides reporting and analytics, including email open rates, click-through rates, and bounce rates.

  • It offers A/B Testing.

  • It offers DMARC analytics.

  • It checks if your IP address is on any blacklists.


  • Enables previewing of emails across browsers and devices to ensure correct rendering for all recipients.

  • Checks email HTML code to ensure it meets coding standards.

  • Tests email content against various spam filters to improve deliverability rates.

  • Evaluates sender reputation score to ensure it's not negatively impacting email deliverability.

  • Provides detailed reporting and analytics.

  • Allows A/B testing to compare the performance of two email campaigns.

  • Offers actionable recommendations on how to improve email campaigns to increase engagement rates and deliverability.

  • Provides insight into DMARC compliance to ensure email authentication and security.

  • Checks if the IP address is on any blacklists, which can negatively impact email deliverability.


  • The tool may offer limited accuracy in predicting subject line effectiveness.


Send Check It is available completely free of cost.


subject line AI testing software - CoSchedule

CoSchedule's email subject line tester uses an AI-powered algorithm to analyze subject lines based on several factors. The tool identifies and suggests words that increase the open rate of your email, such as attention-grabbing, action-oriented, and personalized words. 

Additionally, it also suggests words that decrease the open rate of your email, such as spam triggers, irrelevant, and generic words. 

It further analyzes the length of your subject line, the number of words used, and the presence of emojis, providing recommendations for optimization. The tool also looks for the presence of numbers in your subject line, as they are a great way to increase open rates.


  • CoSchedule provides a visual calendar that allows businesses to view all their marketing activities, campaigns, and deadlines.

  • CoSchedule's project management tools allow teams to collaborate on marketing projects, assign tasks, set deadlines, and track progress.

  • It enables businesses to schedule social media posts across multiple platforms, including Facebook, Twitter, LinkedIn, and Instagram.

  • CoSchedule integrates with popular email marketing tools like Mailchimp and Constant Contact, allowing businesses to schedule and manage their email campaigns from within the CoSchedule platform. 

  • It offers an email subject line tester.

  • CoSchedule provides analytics and reporting.

  • It provides workflow automation tools.

  • CoSchedule integrates with a wide range of marketing tools.


  • Identifies and suggests attention-grabbing, action-oriented, personalized words and relevant numbers to increase email open rates.

  • Helps avoid spam trigger words, irrelevant words, and generic words that may decrease email open rates.

  • Provides recommendations for optimizing the length and content of subject lines.

  • Offers a visual calendar that allows businesses to view all their marketing activities, campaigns, and deadlines in one place.

  • Allows scheduling of social media posts across multiple platforms, including Facebook, Twitter, LinkedIn, and Instagram.

  • Provides detailed analytics and reporting to track the performance of marketing campaigns and make data-driven decisions.

  • Helps businesses automate repetitive tasks, freeing up time for more strategic activities.

  • Allows teams to work together seamlessly, improving communication and productivity.

  • Integrates with a wide range of marketing tools, including Google Analytics, Hubspot, and WordPress.

  • Offers a free Headline Analyzer tool to help businesses write attention-grabbing headlines that drive traffic and engagement.

  • Provides an email subject line tester tool to help businesses optimize their email subject lines for better open rates.

  • Offers a Social Message Optimizer tool to help businesses write social media messages that drive engagement and clicks.


  • The tool's interface could be improved as it may not be the most user-friendly.


subject line AI testing software Coschedule pricing

Email Subject Line Grader

subject line AI testing software - Email Subject Line Grader

Net Atlantic has introduced an Email Subject Line Grader Tool. The scoring algorithm considers word choice, word type, line length, character length, headline type, and other factors to predict potential responses and actions of email recipients.


  • The tool evaluates your email subject line based on different factors such as length, relevance, and actionability and provides you with a grade.

  • Based on the analysis, the tool provides suggestions on improving your email subject line and making it more effective.

  • The tool allows you to compare your email subject line with others in the same industry or category.

  • The tool provides actionable feedback on your email subject line.

  • The tool allows you to customize your analysis based on your specific needs and preferences, such as your industry or target audience.


  • Allows businesses to compare their email subject lines to see how they stack up against the competition.

  • Provides feedback on email subject lines, explaining why they received a particular grade and how they can be improved.

  • Allows customization for better analysis considering personal preferences and requirements.

  • Easy to use and requires no technical expertise, making it accessible to everyone.


  • The tool provides less detailed analysis compared to other subject line tester tools.


Users can access the tool for free.


subject line AI testing software - Omnisend logo

This subject line testing AI software evaluates the subject line based on an emotional analysis score, deliverability assessment, and benchmarking data. The emotional analysis algorithm evaluates the impact of the subject line on the reader, taking into account factors such as sentiment, power words, and word choice. 

The deliverability assessment evaluates the likelihood of the email being delivered to the recipient's Inbox based on factors such as the length of the subject line and the use of spam trigger words. The benchmarking data compares the subject line against industry standards, helping businesses identify areas for improvement.

For example, let's say a business creates a subject line for an email campaign that reads, "Get your holiday shopping done with our new collection". After entering this subject line into Omnisend's Subject Line Tester, the tool provides an emotional analysis score of 8 out of 10, a good deliverability assessment, and above industry standard benchmarking data. 

While the tool suggests that the subject line is already strong, it provides minor changes to optimize it further, such as "Shop our new collection for the holidays and beat the rush".

The updated subject line incorporates urgency and a call to action, encouraging readers to open the email and make a purchase, which can improve the email campaign's effectiveness.


  • Omnisend offers marketing automation that allows businesses to automate their marketing campaigns. 

  • It allows you to segment your audience based on various criteria, such as demographics, behavior, and purchase history.

  • With Omnisend, you can create customizable signup forms and popups. You can use these forms and popups on your website, social media channels, and other marketing channels.

  • Omnisend provides reporting and analytics.


  • Allows for comprehensive marketing automation across multiple channels.

  • Offers segmentation and personalization options for targeted campaigns.

  • Provides customizable signup forms and popups to capture more leads and grow email lists.

  • Offers a product recommendation engine to increase sales and improve customer engagement.

  • Provides detailed reporting and analytics to optimize campaigns and improve marketing ROI.


  • Limited email design options.


subject line AI testing software Omnisend pricing


subject line AI testing software - Isnotspam

ISnotSPAM is an AI subject line tool tester which not only tests the contents of your email but also your subject lines using five different tests, including SPF and Sender-ID checks


  • You can preview your email across various browsers and devices to ensure it is optimized for all platforms.

  • It offers HTML validation.

  • It allows you to view your email's deliverability rates.

  • ISnotSPAM provides a score for your email sender reputation.

  • You can view detailed reports and analytics on your email campaigns' performance.

  • Based on the testing results, ISnotSPAM provides recommendations to improve your email's performance.

  • It offers DMARC (Domain-based Message Authentication, Reporting & Conformance).

  • ISnotSPAM checks your IP address against various blacklists.


  • Helps email marketers test their email content for spam characteristics to ensure deliverability.

  • Allows pre-send email testing to identify and fix issues before sending emails to subscribers.

  • Enables previewing of emails across various browsers and devices to ensure optimization for all platforms.

  • Identifies and fixes any HTML issues in email code to ensure deliverability.

  • Uses various spam filters to test email content and provide suggestions to improve deliverability rates.

  • Offers detailed reports and analytics on email campaign performance.

  • Allows A/B testing to identify the most effective approach.

  • Allows monitoring of DMARC reports to ensure proper authentication.

  • Checks IP addresses against various blacklists to identify and resolve any potential issues.


  • The customization options are limited.

 The Advanced Marketing Institute Headline Analyzer 

subject line testing AI software - Advanced Marketing Institute's Headline Analyzer

Advanced Marketing Institute's proprietary analysis technology is designed to examine your headline and assess its Emotional Marketing Value (EMV) score for free.

After analyzing your headline, Advanced Marketing Institute's tool will calculate an EMV score based on the number of EMV words it contains relative to the total word count. 


  • The tool uses a proprietary algorithm to calculate the Emotional Marketing Value of your headline, which is a measure of how emotionally engaging it is likely to be for readers.

  • The tool analyzes your headline based on its structure, grammar, and language usage.

  • Based on the analysis, the tool provides you with suggestions for words to include or remove.

  • The tool analyzes your headline to identify keywords likely to resonate with your target audience.

  • The tool allows you to customize the analysis based on your specific industry or target audience.


  • Utilizes proprietary analysis technology to examine headlines and assess their Emotional Marketing Value (EMV) score for free.

  • Calculates EMV score based on the number of EMV words in relation to the total word count and identifies which emotion - intellectual, empathetic, or spiritual - the headline most effectively elicits from the audience.

  • Analyzes headlines to identify keywords to improve SEO.

  • User-friendly and requires no technical expertise, making it accessible to everyone.


  • The tool's analysis of subject lines may lack detail compared to other subject line testers.


Users can access the tool at no cost.


subject line testing AI software - Touchstone

Touchstone is an email marketing tool that provides businesses with a range of advanced features to help them improve their email campaigns; however, it’s not a free platform. Using this tool, you can evaluate subject lines against a comprehensive database of more than 21 billion emails.

You have two options, a single-day package that offers testing for an unlimited list size or a monthly package that allows you to test up to 250,000 email addresses.


  • The tool enables users to test subject lines by conducting segment testing, which involves testing different subject lines with different groups of subscribers.

  • The tool provides full reporting dashboards that enable users to track the performance of their email subject lines. The dashboards provide detailed analytics, including open rates, click-through rates, and conversion rates.

  • The tool provides access to Touchstone's database, which contains data from millions of emails across various industries. 


  • Allows users to evaluate subject lines against a comprehensive database of more than 21 billion emails, enabling email marketers to optimize their subject lines to improve open rates and engagement.

  • Offers segment testing, allowing marketers to identify the best-performing subject lines for different email list segments.

  • Provides full reporting dashboards with detailed analytics, enabling users to track the performance of their email subject lines.

  • Provides access to Touchstone's database, allowing marketers to benchmark their email subject lines against industry standards and best practices.


  • It is an expensive tool.

  • Beginners may need help in learning.


subject line AI testing software Touchstone pricing


subject line testing AI software - Mailmeteor

The Email Subject Line Tester is a cost-free resource anyone can use to examine their email subject line. It evaluates whether the email subject line is well written, has appropriate length, and is free of spam-related content. 

The email subject line will receive a lower score if any issues are recognized.


  •  Mailmeteor enables users to create and send personalized email campaigns to their contacts. Users can customize email content and subject lines based on their contact's name, location, or other personal details.

  • The tool allows users to send mass emails to a large number of contacts at once.

  • Mailmeteor provides email tracking features. Users can monitor email opens, clicks, and replies.

  • The tool includes templates enabling users to create professional-looking emails quickly. Users can choose from a variety of templates or create their own using Mailmeteor's intuitive editor.

  • Mailmeteor allows users to manage their contacts. Users can add, remove, or edit contacts easily and organize them into groups for targeted campaigns.

  • The tool provides scheduling features that allow users to schedule their emails for a specific time and date.

  • Mailmeteor enables collaboration, allowing users to share email templates, campaigns, and contacts with team members.

  • Mailmeteor provides mail merge features that enable users to send customized emails to multiple recipients at once.


  • Allows users to send mass emails to a large number of contacts at once, saving time and effort.

  • Provides email tracking features that enable users to monitor email opens, clicks, and replies to make data-driven decisions to improve campaign performance.

  • Includes customizable email templates that enable users to create professional-looking emails quickly.

  • Provides scheduling features that allow users to schedule their emails for a specific time and date to reach their contacts at the right time for maximum impact.

  • Complies with GDPR regulations, ensuring that users' email campaigns are in line with data protection laws and regulations.

  • Provides mail merge features enabling users to send customized emails to multiple recipients simultaneously, saving time and effort.


  • Paid or premium versions of the tool are required to attach documents.


subject line AI testing software MailMeteor pricing

Spam Check by Postmark

subject line testing AI software - spamcheck

Postmark is an email delivery service that provides a spam check feature to improve the deliverability of emails sent through their platform. One of its unique features is its spam score. 

This feature isn't just limited to subject lines – you can input your entire email content and get a comprehensive score that will help improve the message's chances of reaching your target audience. 


  • Postmark offers a spam check feature that evaluates both the subject line and email content to identify any red flags that might trigger spam filters.

  • It provides a detailed analysis of your email content, including recommendations on how to improve your score, helping you optimize your email campaigns.


  • With a better spam score, your email has a higher chance of reaching your target audience, which can result in increased open and click-through rates.

  • By receiving detailed analysis and recommendations on how to improve your email content, you can optimize your campaigns and achieve better results over time.

  • Using Postmark's spam check feature, you can proactively improve your email deliverability rather than simply reacting to issues as they arise.


  • The email subject line personalization, sentiment, or readability analysis must be improved to enhance user experience.


The tool is free of cost.

Maximize open rates with these email subject line tips 

Have you ever thought about how many emails your customers receive each day? It’s a lot. And while many of them are likely to be relevant to their interests, they’ll still need something extra to get them to open yours.

 That’s where the email subject line comes in. It’s one of the most important elements of an email and can make or break whether someone opens your email or not. 

Here’s how you can use it to increase your open rates. 

Keep it straightforward 

The first tip for crafting a successful subject line is to keep it straightforward. You don't want it too long and make sure that each word is descriptive and relevant to the content of the email itself. 

This will help ensure that both search engine robots and recipients understand the email and why they should open it. 

Personalize it 

One way to make sure that your subject lines perform better than the hundreds of other emails that prospects receive each day is by personalizing it with their name or other information specific to them. 

 For example, if you were sending an email to a customer named Sarah about a special discount on her favorite product, your subject line could read, "Sarah, don't miss your exclusive 20% off on [favorite product] just for you!" 

This personal touch grabs her attention and demonstrates that you are attentive to her preferences and interests, increasing the likelihood that she will open and engage with the email.

Avoid spammy words 

subject line testing Ai software notices spammy words

You should also avoid using words in your subject lines that may trigger spam filters or otherwise repel subscribers, such as “free” or “pay now” or even characters like % or *. 

Using these words can cause your emails to be flagged as spam and sent straight into people's junk folders instead of their inboxes, greatly reducing your chances of getting those all-important open rates up!

Run A/B testing 

If you're unsure which type of subject line works best for your audience, try running A/B testing campaigns where you send out two slightly different versions of an email with different subject lines and compare which version performs better. 

This will give you insight into what subjects resonate with readers more than others, allowing you to craft even better ones in the future! 

Optimize for mobile devices 

Your subject lines should also look good on mobile devices since more people use smartphones than ever to access their emails. Make sure that any text in your subject line isn't too long so that it fits nicely on smaller screens without being cut off.

Additionally, if you're including emojis, think about how they'll look on different devices before sending out your campaign. 

Combine with sender name/preheader text

Finally, remember to include additional elements such as the sender name and preheader text in order to optimize open rates even further! 

The sender name helps people identify who sent them the email (which might be helpful if they receive multiple emails from different companies), and preheader text provides additional context for what's inside the message itself (which can help encourage people who may not have opened it otherwise).   


The subject line is like the opening act of a concert - it sets the tone for the whole experience. So make sure your email isn't a one-hit wonder that leaves your subscribers feeling disappointed.

Bottom line

To conclude, it is clear that artificial intelligence software has the potential to revolutionize how we conduct subject-line testing, resulting in more compelling subject lines. It eliminates guesswork and provides meaningful data-driven insights with minimal effort and cost.

This makes it an invaluable tool for any business that wants to optimize its success through improved marketing strategies. 

By leveraging AI, businesses can focus on refining their messaging based on real metrics – translating into higher open rates, higher engagement rates, and ultimately more conversions. 

However, an effective email marketing campaign can have a significant impact on your brand's credibility, expand your customer base, and help you turn leads into sustainable income.

That’s why you need an excellent email marketing service that has all the essential features with some extras that make the whole process much simpler and more effective.

GoCustomer has a variety of features such extreme personalization as A/B testing, email domain warmup, email verification, and an AI email writing assistant. 

Sign up today for access to all of these wonderful features at a very affordable price. 

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Reach more customers with your cold emails

Table of Contents

    In a nutshell

    Subject lines are the first thing your target audience sees when an email lands in their Inbox and determine the open rate. If your email is not opened, it can never lead to a conversion.
    Subject lines also affect email deliverability. If the subject line includes spammy words, punctuation, etc. the email is likely to go into spam rather than the prospects' Inbox.
    Testing tools determine whether the subject line is optimal in length, with the types of emotions it triggers, whether it is using power words, and whether it is click-worthy.
    No, subject line testing AI software does not always have to be accurate as predictive analytics are used to determine whether a subject line would be attractive to a target audience. If you are personally confident about your subject line, you may want to simply go for it!
    If a subject line is too long it won't fit on mobile screens or will get cut off when the email shows up in the recipients' Inboxes.
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